Dual function high efficiency water heater

ABSTRACT

This gas-fired water heater has a shell sealed at opposite ends within an insulated storage tank, defining a water-tight chamber with inlet and outlet water connections thereto. The shell preferably is a one-piece casting of aluminum alloy, with a circular array of impervious passages between its opposite ends. Each passage is defined by a curved wall segment spaced inwardly adjacent the tank and a pair of side walls converging inwardly from opposite ends of each curved wall segment to an inboard corner, where the adjacent corners and side walls are spaced apart radially and circumferentially respectively yielding water contact against all exterior passage surfaces. A burner under the storage tank generates hot flue gases that vent through the passages for heating the chamber water. A rib can project inwardly from the curved wall segment into each flow passage, adding heat transfer to the wall segment and contacted water.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

1. Technical Field of Invention

This invention relates to a water heater in which combustion products are caused to flow past a tank to heat water in the tank, particularly for domestic use such as showering and washing the dishes or clothes, as well as for space heating in a building.

2. Description of the Prior Art

In a conventional gas fired/fueled water heater of prior art U.S. Pat. Nos. 4,672,919; 5,020,512; 5,199,385; 5,335,646, etc., a gas burner is located beneath the lower end of the water tank in a combustion chamber. A central vertical flue pipe is provided through the tank for discharge of the waste combustion or flue gases. Water in the tank is heated by the heat from the burner in the combustion chamber and from the waste gases passing upward through the central flue pipe, which serves as a heat transfer surface for heating water. Different flue baffles are placed into the flue pipe to increase the amount of heat transmission through the flue pipe. The thermal efficiency of such water heaters is usually 76-80%. The reason for such a low thermal efficiency is the high temperature of the outlet flue gases, which can reach 200° C.

A multi-flue construction can be used to increase the productivity of water heaters (e.g. by U.S. Pat. Nos. 4,157,077; 4,512,289; 4,531,509; 5,027,749). However, these constructions are very complicated, generally being expensive and complex, and contain numerous welds, which shorten a water heater's life. Moreover, special means are required to prevent sediment buildup the tank, e.g. as in U.S. Pat. No. 5,341,770.

Furthermore, it is known that hot water heaters may have two separate hot water outlets, one for domestic hot water and the other for a heating system in a building. Examples of such devices are shown in U.S. Pat. Nos. 2,937,625; 4,222,350; 5,228,413; 5,372,185.

3. Object and Advantages of the Invention

It is an object of the present invention to provide a water heater with a constant thermal efficiency of 85-95% during a heater's life, for residential use as well as for commercial use with a manufacturing cost that is not greater than other ordinary residential models of the same productivity and much less than the cost of ordinary commercial models.

The current invention provides the following advantages:

-   -   1) Increased water heater operating efficiency to 85-95%, by         improving heat recovery from flue gases to water.     -   2) Increased water heater power, without decreased operating         efficiency and without increased water heater dimensions.     -   3) Simple construction, easily implemented at low cost.     -   4) Replacement of a typically separate water heater and boiler         with a single unit, by performing dual functions such as         showering and washing the dishes or clothes, as well as a         heating system in a building.     -   5) Reduced cost for water heating, by improving heater         efficiency during the water heater's life and by dual function         implementation.     -   6) Prolonged water heater lifespan, by eliminating sediment         accumulation within the water heater tank.

Other objects and advantages of the present invention will become apparent to those skilled in the art from the drawings, the detailed description of the preferred embodiment, and the appended claims.

BRIEF SUMMARY OF THE INVENTION

There is a need for a dual function, relatively simple, and highly efficient water heater in which combustion products are caused to flow past a tank to heat water. In accordance with the present invention, a water heater is provided that includes an insulated water tank with a flue pipe extending vertically through the tank for the discharge of waste combustion or flue gases, a burner below the tank, and a burner control means. The flue pipe comprises a water-surrounded and radially-expanded means for increasing heat recovery from the flue gases. The radially-expanded means comprises a chamber for the flow of the flue gases. The chamber includes a means for directing the flue gases toward the inner surface of the radially-expanded means. In a further improvement, the water heater comprises a means for transferring heat from the water in the tank to an additional water line, preferably for heating potable water for domestic use such as showering and washing the dishes or clothes. In a still further improvement (FIG. 1 c), the burner control means possesses an additional means for adjusting burner power depending on water temperature in the water tank.

In accordance with the invention, in the second alternative preferred embodiment as shown in (FIG. 1 a, FIG. 1 b, and FIG. 1 c), the means for directing the flue gases constitutes a tank containing water in a heat exchange relationship with the water in the main heater tank of the water heater. In a still further modification (FIG. 1 c), the tank for directing the flue gases comprises at least two interconnected sections.

In accordance with the invention, the third alternative preferred embodiment (FIG. 2 and FIG. 3) provides a water heater having an additional heat exchanger for heating water for potable use, a burner with control means, and a water housing containing the water to be heated. The water housing comprises an inner ribbed means and a separate outer shell tightly interconnected and sealed together, between which is contained the water to be heated and the heat exchanger. In the preferred embodiment, the outer shell is in the shape of a cylinder with one partially closed top end and one open bottom end. The partially closed top end possesses a machined flange face sealing surface on the inside surface of the top end, and the open bottom end possesses a machined flange face sealing surface on the bottom side of a lip perpendicularly extending from the outside of the outer shell. The inner ribbed means is preferably in the shape of a truncated cone with one partially closed top end and one open bottom end. The partially closed top end possesses a machined flange face sealing surface on the outside surface of said top end, and said open bottom end possesses a machined flange face sealing surface on the top side of a lip extending from the outside of the inner ribbed means. The flange face sealing surface on the top end of both the inner ribbed means and outer shell are tightly sealed and connected together, and the flange face sealing surface on the lip of the bottom end of both the inner ribbed means and outer shell are tightly sealed and connected together. The opening of the partially closed top end of both the inner ribbed means and outer shell provides for the discharge of the combustion gases from the water heater, and the opening of the bottom end of the inner ribbed means provides for the entry of the hot combustion gases to the water heater.

In a further improvement, the burner control means possesses an additional means for adjusting burner power, depending on water temperature in the water housing.

In a still further improvement, the inner ribbed means constitutes a cast shell comprising a plurality of ribs for absorbing and transferring heat from the combustion gases.

In a still further improvement, the ribs are radially-starlike situated in the inner cast shell.

In a still further improvement, at least some of the ribs possess inner water cooling passages to maximize heat transfer.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

In the drawings which illustrate the present invention,

FIG. 1 is an elevated cross-sectional view showing a first preferred embodiment of a water heater according to the present invention.

FIG. 1 a is an elevated cross-sectional view illustrating a second preferred embodiment of a water heater according to the present invention.

FIG. 1 b is an elevated cross-sectional view illustrating a similar embodiment to FIG. 1 a.

FIG. 1 c is an elevated cross-sectional view illustrating a second similar embodiment to FIG. 1 a.

FIG. 2 is a side elevated cross-sectional view illustrating a third preferred embodiment of the water heater according to the present invention.

FIG. 3 is a top cross sectional view taken along line A-A of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The detailed description is presented to illustrate the present invention but is not intended to limit it.

In more detail, a typical water heater, in which combustion products are caused to flow past a tank to heat water in the tank, comprises a gas burner located beneath the lower end of the tank in a combustion chamber. A central vertical flue pipe is provided through the tank for discharge of the waste combustion or flue gases. Water in the tank is heated through the bottom end of the tank by the heat from the burner in the combustion chamber and from the waste gases passing upwardly through the central flue pipe, the walls of which also serve as a heat transfer surface for heating water. In order to increase the amount of heat transmission through the flue pipe, and to increase the productivity and efficiency of the water heater, a preferred embodiment of a water heater is shown best in FIG. 1. According to the invention, the improved water heater includes a water chamber 21 surrounded by a typical cylindrical tank 11 with upper concave shaped end 22 and lower convex shaped end 14. The water tank 11 having a water inlet stub pipe 31 leads to the lower portion of the tank, and water outlet stub pipe 30 located at the upper end 22 of tank 11 is surrounded by a layer of insulation 32 on the side and top. An outer jacket 33 surrounds the insulation 32 to protect it from mechanical damage. A burner 12 situated in a burning chamber 13 and located under the lower end 14 of the tank 11 is adapted to combust gas such as natural gas or propane or some other combustible material such as oil. While the invention is disclosed in respect to a gas-fired water heater, it is equally applicable to water heaters which burn other combustible fuels. Such water heaters are intended to fall within the scope of the claims. A cylindrically shaped steel flue pipe 16 passes through the bottom end 14 extending vertically through the tank 11 for removing flue gases from the burning chamber 13. The concave shaped bottom end 14 directs hot gases into the flue pipe 16. The flue pipe 16 comprises a water surrounded inner tank (means) 18 for increasing heat recovery from the flue gases. The water surrounded inner tank 18 in the shape of a boiler drum with openings in the covers 19 and 20 is welded on a part of the length of the flue pipe 16, dividing the flue pipe 16 into two separate pieces 16 a and 16 b. The inner tank 18 comprises a chamber 18 a for the flow of the hot flue gases, and the chamber 18 a comprises a thin-walled steel container (means) 25 for directing the flue gases toward the inner surface of the water surrounded inner tank 18. The thin-walled steel container (means) 25 is in a shape similar to the water surrounded inner tank 18 and is filled with thermal insulation 26. The container is equipped with two spacers 27 and 27 a for its central positioning in the water surrounded inner tank 18. The water heater also comprises a copper helically coiled heat exchanger 17 for transferring heat from the water in the water chamber 21 to an additional water line, preferably for heating water for domestic use such as showering and washing the dishes or clothes. A helically coiled heat exchanger 17 is placed in the water space between the top ends 20 and 22 of the two cylindrical pressure tanks 11 and 18 and is connected to couplings 23 and 24 which are welded into the top end 22 of the outer water tank 11. The stud pipes 30 and 31 of the outer water tank 11 allow connectivity to the home's heating system. The water heater contains a typical gas burner 12 placed in the burner chamber 13. The gas burner 12 is operated with an improved burner control means 15 similar to a typical gas control valve. The burner control means 15 possesses an additional valve (means) (not shown) for adjusting the power of the burner 12 depending on water temperature in the water tank 11, whereby increasing the efficiency of the water heater. The outer jacket 33 surrounding the insulation 32 also constitutes a base 34 supporting the water heater construction over the floor's surface. The lower uninsulated part of the base 34 possesses air flow openings 35 supporting the gas burning process in the burning chamber 13.

Heated combustion gases produced by the burner 12 impinge against the bottom 14 of the outer tank 11 to cause heat transfer therethrough to the water in the chamber 21. The hot burned gases further rise upward from the burning chamber 13 through the opening 36 in the flue pipe 16 a to the chamber 18 a of the inner tank 18 where they flow along the walls of the inner tank 18 to the flue pipe 16 b allowing the gases to flow out from the water heater to a chimney (not shown).

A second alternative embodiment of the water heater according to the invention is shown in FIG. 1 a, FIG. 1 b, and FIG. 1 c. The alternative embodiments are similar to the embodiment shown in FIG. 1. In the second alternative embodiment, the means 25 for directing the flue gases toward the inner surface of the inner tank 18 constitutes a tank containing water in a heat exchange relationship with the water in the water chamber 21. The tank 25 directing the flue gases is connected in a flow-through manner to the water in the water chamber 21 with two pipes—an inflow pipe 28 and an outflow pipe 29. As shown in FIG. 1 a, the inflow pipe 28 is connected to the water chamber 21 with an inflow stub tube 31 and the outflow pipe 29 is connected to the water chamber 21 with an outflow stub tube 30 delivering the hot water to the home heating system (not shown). As shown in FIG. 1 b, the inflow pipe 28 of the tank is connected to the water chamber 21 through the concave bottom end 14 of the tank 11. As shown in FIG. 1 c, the tank (means) 25 directing the flue gases toward the inner surface of the inner tank 18 comprises three interconnected sections 25 a. Such a structure further increases contact area between flue gases and the water surrounded walls to maximize heat transfer.

The water heater as shown in FIG. 1 c, comprises an additional control means 15 a situated on the side of the water heater and connected to the main burner control means 15. The additional control means 15 a, constitutes a temperature sensor that sends a signal to the additional gas control valve (not shown) in the burner control means 15 depending on the water temperature in the water chamber 21 to adjust the power of the burner 12.

In a third alternative embodiment of the water heater shown in FIG. 2 and FIG. 3, the water heater comprises a heat exchanger 17, a burner 12 with a burner control means 15 and a water housing 10. The water housing 10 comprises a separate inner cast shell 41 (inner ribbed means) and separate outer shell 40, which are tightly sealed and interconnected on their ends 42, 44 and 43, 45. The chamber 21 between the inner cast shell 41 and the outer shell 40 contains circulated water to be heated and a heat exchanger 17, which constitutes a copper pipe helically coiled around the inner cast shell 41. The inner cast shell 41 comprises sixteen ribs 48 for absorbing and transferring heat from the combustion gases to the circulated water, which is located in the chamber 21 between shells 40 and 41. Eight of the ribs 48 possess channels 49 filled with circulating water to maximize heat transfer from the flue gases. The ribs 48 are radially placed, starlike, in the inner cast shell 41. The inner cast shell 41 made out of an aluminum alloy is in the shape of a truncated cone with one partially closed top end 45 and one open bottom end 44. The partially closed top end 45 possesses a machined flange face sealing surface on the outside surface of the top end 45. The open bottom end 44 also possesses a machined flange face sealing surface on the top side of the lip extending out from the bottom end 44.

The outer shell 40 made of cast iron is in the shape of a cylinder with one partially closed top end 43 and one open bottom end 42. The partially closed top end 43 possesses a machined flange face sealing surface on the inside surface of the top end 43. The open bottom end 42 possesses a machined flange face sealing surface on the bottom side of a lip 42 that perpendicularly extends from the outside of the bottom end 42 of the outer shell 40.

The flange face sealing surface on the top end of both shells 40 and 41 are connected together with bolts 46 and sealed with a sealing ring 47 a installed between the sealing surfaces.

Also the flange sealing surface on the lip of the bottom end 42 and 44 of both shells 40 and 41 are connected together with the same kind of bolts 46 and sealed with a sealing ring 47 located between their sealing surfaces.

The coiled heat exchanger 17 is connected to the inflow and outflow couplings 23 and 24 placed in the partially closed top end 43 of the cast iron outer shell 40. The water heated by the exchanger 17 is for potable use.

The outer shell 40 also includes two stub tubes 30 and 31 for connecting to a heating system in a building (not shown). The water heater contains a typical gas burner 12 placed in the burning chamber 13, which is controlled with an improved gas control valve 15 placed on the side of the outer shell 40. The improved gas control valve possesses an additional valve (not shown) for adjusting the power of the burner 12 depending on water temperature in the water chamber 21. The outer shell 40 is surrounded by a layer of insulation 32 on the side and top. An outer jacket surrounds the insulation 32 to protect it from mechanical damage. The outer jacket 33 also constitutes a base 34 supporting the water heater construction over the floor's surface. The lower uninsulated part of the base 34 possesses air flow openings 35 supporting the gas burning process in the burning chamber 13.

Hot combustion gases produced by the burner 12, in the burning chamber 13, impinge against the ribbed surface 50 of the inner cast shell 41, which allows for heat transfer therethrough to the water in the chamber 21. The hot burned gases rise upward along the ribs 48 and ribbed surface 50, transmitting its heat through the walls 51 (FIG. 3) to the water chamber 21. The flue gases flow out through the flue channels 52 to the pipe 53 and outside to the chimney (not shown). 

1-27. (canceled) 28-35. (canceled)
 36. A gas-fired natural draft water heater, comprising the combination of a vertically aligned insulated cylindrical water-tight sealed storage tank having lower and upper headers, a burner underlying the lower header operable to generate hot flue gases, and cold water inlet and hot water outlet connections in the tank for conveying water there through; a water-tight thermally conductive flue pipe extending axially and generally concentrically of the storage tank between sealed end connections in the headers for conveying the flue gases through the tank, with the water in the tank being annular of and substantially contacting all of the exterior surfaces of the flue pipe; said flue pipe having inlet and outlet end segments sealed to the headers and an intermediate segment larger in cross-section than the end segments; said intermediate segment being continuous and comprised of consecutive upstream, intermediate and downstream contours, where said intermediate contour extends axially of the cylindrical tank, and said upstream and downstream contours are extended transversely of the cylindrical tank; and an impervious baffle mounted in the intermediate flue pipe segment and disposed transversely of the cylindrical tank, with the baffle peripheral edge being spaced from the intermediate contour of the flue pipe segment operable for defining an annular flue gas flow path around the baffle and transversely of the tank wall for increasing heat transfer between the flue gas and adjacent tank water.
 37. A water heater according to claim 36, further comprising a coiled pipe in the annular chamber for absorbing and transferring heat from the hot water contained in said chamber to an additional water line.
 38. A gas-fired water heater, comprising the combination of a vertically aligned insulated generally cylindrical storage tank, an inner shell within the tank, means sealing the shell and tank together at respective lower and upper ends whereby a closed water-tight chamber is defined therebetween, and inlet and outlet connections for the chamber operable to convey water there through; said shell having a circular array of impervious axially extended passages between the lower and upper chamber ends, each passage being defined by exterior walls including a curved wall segment spaced inwardly adjacent the tank and a pair of side walls converging inwardly from the opposite ends of each curved wall segment to meet at an inboard liquid-tight corner, and the adjacent passage side walls and inboard corners being circumferentially and radially separated respectively defining starlike extensions of the chamber whereby chamber water can contact all of the exterior passage surfaces; and a burner underlying the storage tank operable to generate hot flue gases; and headers adjacent respective lower and upper open ends of the passages for conducting said flue gases through the passages and away from burner and the water heater.
 39. A water heater according to claim 38, further comprising a radial rib extended inwardly from the curved wall segment into each flow passage, adding heating exposure to the wall segment from flue gases passing through the passages.
 40. A water heater according to claim 38, further comprising the curved wall segments together having their exterior surface shaped in general as a truncated cone smaller at
 41. A gas-fired water heater according to claim 38, further comprising the inner shell being cast as a single piece of an aluminum alloy.
 42. A water heater according to claim 38, with said means sealing the shell and tank together comprising the shell having an annular partially closed top end wall and an outwardly projected annular bottom end lip, and said tank overlying said shell and having an annular top end wall and an annular bottom end flange suited to butt flush against said shell top end wall and said bottom end lip, and means securing the end walls and said lip and flange together in sealed association.
 43. A water heater according to claim 38, further comprising a radial rib extended inwardly from the curved wall segment into each flow passage, adding heating exposure to the wall segment from flue gases passing through the passages, and the curved wall segments together having their exterior surface shaped in general as a truncated cone smaller at the upper end.
 44. A gas-fired water heater according to claim 43, further comprising the inner shell being cast as a single piece of an aluminum alloy.
 45. A water heater according to claim 44, with said means sealing the shell and tank together comprising the shell having an annular partially closed top end wall and an outwardly projected annular bottom end lip, and said tank overlying said shell and having an annular top end wall and an annular bottom end flange suited to butt flush against said shell top end wall and said bottom end lip, and means securing the end walls and said lip and flange together in sealed association.
 46. A water heater according to claim 44, further comprising a coiled pipe in the annular chamber for absorbing from the hot water contained in said chamber, and inlet and outlet connections through the tank operable to convey an additional water line to the coiled pipe. 